Current thinking suggests that two cochlear sources contribute to distortion product otoacoustic emissions (DPOAEs), a distortion source and a reflection source. In contrast, low-level stimulus frequency OAEs (SFOAEs) are believed to be dominated by reflection-source contributions. It has been proposed that DPOAEs would more accurately predict behavioral threshold and identify auditory status if the reflection-source contribution is reduced or eliminated, although this hypothesis has not been tested. The broad objective of the proposed study is to determine the influence of cochlear-source contribution on OAE test performance. Four specific aims are posed. 1) The most effective suppressor tone for reducing the reflection-source contribution to DPOAEs will be determined. 2) Accuracy in predicting behavioral thresholds from traditional (two-source) DPOAEs, distortion-source DPOAEs (reflection source suppressed), and SFOAEs, will be evaluated in normal and impaired human ears. 3) Clinical decision theory will be used to evaluate the accuracy with which dichotomous decisions regarding auditory status are made with two-source (traditional DPOAEs) and single-source OAEs (distortion-source DPOAEs and SFOAEs). 4) The role of fine structure (thought to arise from the complex summation of distortion- and reflection-source energy for DPOAEs) in prediction and diagnostic errors will be evaluated.